The industrial use of enzymes, notably enzymes of microbial origin, has become increasingly common. Enzymes are used in numerous industries, including, for example, the starch-processing industry and the detergent industry. It is well known that the use of enzymes, particularly proteolytic enzymes, in the detergent industry has given rise to industrial hygiene concerns for detergent factory workers, particularly due to the health risks (including the risk of allergy development) associated with any formation of enzyme-containing dust which may occur.
Since the introduction of enzymes into the detergent industry, a lot of effort has been devoted to improving the granulation and coating of enzymes so as to reduce enzyme dust formation.
One type of process for producing an enzyme-containing granule comprises coating the surface of a core with an enzyme followed by an outer layer coating. U.S. Pat. No. 5,324,649 describes coating of the surface of a non-pareil core with an enzyme followed by an outer layer coating. U.S. Pat. No. 4,689,297 and EP 0 532 777 describe a process which comprises applying an enzyme on the surface of a salt crystal based core or a non-pareil core, by spraying the enzyme onto the core in a fluid-bed followed by an outer layer coating.
Yet another type of process essentially comprises: (i) mixing an enzyme with suitable granulation components (preferably as dry matter), such as filler, binder, fibrous material and a granulation agent (e.g. water) in a granulator (e.g. a mixer), and (ii) processing the mixture in a granulating apparatus until the granule has the desired particle distribution and degree of roundness (sphericity).
Numerous references describe processes for making enzyme-containing granules by such a process. Such references include U.S. Pat. No. 4,242,219, U.S. Pat. No. 4,740,469, WO 94/04665, U.S. Pat. No. 4,940,665, EP 564476, EP 168526, U.S. Pat. No. 4,661,452, U.S. Pat. No. 4,876,198, WO 94/16064 and U.S. Pat. No. 4,106,991.
Further, U.S. Pat. No. 5,494,600 and U.S. Pat. No. 5,318,903 describe a process comprising absorption of an enzyme into a porous hydrophobic core (e.g. a porous hydrophobic silica core) followed by coating.
Although granulation techniques have improved, in order to take account of increasing environmental concerns and heightened awareness in the field of industrial hygiene, there remains a continuing need for enzyme-containing, granular compositions exhibiting even lower dust formation than presently available products.
An object of the present invention is to provide such enzyme-containing granular compositions, and improved processes for producing such compositions.